Guidelines for Creating Usable Hierarchies
The data from card sorts can help you design good hierarchies. Here are some additional guidelines that should help you do that.
Allow Things to Exist in Several Places
Keep in mind that hierarchies don’t have to be strict: things don’t have to be in exactly one place inside the hierarchy. You can give users several paths that lead to the same result. This is sometimes called a polyhierarchical classification. There’s an example in Figure 6, Example polyhierarchical classification.
I mentioned a bit earlier that some users who experience problems with ...